Title: Nanotechnology Application for Solar Cells: Using Quantum Dots to Modify Absorption Properties
1Nanotechnology Application for Solar Cells
Using Quantum Dots to Modify Absorption
Properties
- Prepared by
- James Fodor
- Kwok Mak
- Viet Huynh
2Introduction
- How Classical Solar Cells Operate
- Absorption Coefficient (a)
- Definition and Relevance of a
- Physical Techniques for Measuring a
- Light Absorption of Quantum Dot Layers
- Reasons for Interest Into Quantum Dot Light
Absorption - Definition of a Quantum Dot
- Formula for Light Absorption of a Quantum Dot
- Comparison of a versus Energy for Bulk Material
and Quantum Dot - Researchers working on Light Absorption of
Quantum Dots - Dr. Sheila Baily
- Dr. Ryne Raffaelle
- Problem Statement Determining the most
optically absorbent semiconductor material - Problem Solution
- Explanation of Theory
- Results
3Introduction
- How Classical Solar Cells Operate
- Absorption Coefficient (a)
- Definition and Relevance of a
- Physical Techniques for Measuring a
- Light Absorption of Quantum Dot Layers
- Reasons for Interest Into Quantum Dot Light
Absorption - Definition of a Quantum Dot
- Formula for Light Absorption of a Quantum Dot
- Comparison of a versus Energy for Bulk Material
and Quantum Dot - Researchers working on Light Absorption of
Quantum Dots - Dr. Ryne Raffaelle
- Dr. Sheila Baily
- Problem Statement Determining the most
optically absorbent semiconductor material - Problem Solution
- Explanation of Thoery
- Results
4How Classical Solar Cells Operate1,2
5How Classical Solar Cells Operate1,2
6How Classical Solar Cells Operate1,2
7How Classical Solar Cells Operate1,2
8How Classical Solar Cells Operate1,2
9How Classical Solar Cells Operate1,2
10How Classical Solar Cells Operate1,2
11How Classical Solar Cells Operate1,2
12Introduction
- How Classical Solar Cells Operate
- Absorption Coefficient (a)
- Definition and Relevance of a
- Physical Techniques for Measuring a
- Light Absorption of Quantum Dot Layers
- Reasons for Interest Into Quantum Dot Light
Absorption - Definition of a Quantum Dot
- Formula for Light Absorption of a Quantum Dot
- Comparison of a versus Energy for Bulk Material
and Quantum Dot - Researchers working on Light Absorption of
Quantum Dots - Dr. Ryne Raffaelle
- Dr. Sheila Baily
- Problem Statement Determining the most
optically absorbent semiconductor material - Problem Solution
- Explanation of Thoery
- Results
13Absorption Coefficient a Definition and
Relevance of a3
- Definition of Absorption Coefficient a
- A measure of the rate in decrease of
electromagnetic radiation (as light) as it passes
through a given substance the fraction of
incident radiant energy absorbed per unit mass or
thickness of an absorber.
14Absorption Coefficient a Definition and
Relevance of a3
- Unit of Absorption Coefficient a
- The units of a are per length (cm-1)
15Absorption Coefficient a Definition and
Relevance of a3
- Unit of Absorption Coefficient a
- The units of a are per length (cm-1)
16Absorption Coefficient a Definition and
Relevance of a4
- Absorption Versus Transmission
- Transmission (t) a measure of conduction of
radiant energy through a medium, often expressed
as a percentage of energy passing through an
element or system relative to the amount that
entered.
17Absorption Coefficient a Definition and
Relevance of a4
- Absorption Versus Transmission
- Transmission (t) a measure of conduction of
radiant energy through a medium, often expressed
as a percentage of energy passing through an
element or system relative to the amount that
entered.
18Absorption Coefficient a Definition and
Relevance of a4
- Absorption Versus Transmission
- Transmission (t) a measure of conduction of
radiant energy through a medium, often expressed
as a percentage of energy passing through an
element or system relative to the amount that
entered.
19Absorption Coefficient a Physical Techniques
for Measuring a5,6
- Optical Transmission Measurement
- t Measured transmission
- l Sample thickness
- R - Reflectance
20Introduction
- How Classical Solar Cells Operate
- Absorption Coefficient (a)
- Definition and Relevance of a
- Physical Techniques for Measuring a
- Light Absorption of Quantum Dot Layers
- Why We Are Interested
- Definition of a Quantum Dot
- Formula for Light Absorption of a Quantum Dot
- Comparison of a versus Energy for Bulk Material
and Quantum Dot - Researchers working on Nano-coating
- Dr. Ryne Raffaelle
- Dr. Sheila Baily
- Problem Statement Determining the most
optically absorbent semiconductor material - Problem Solution
- Explanation of Theory
- Results
21Light Absorption of Quantum Dots Why We Are
Interested7,8,13
- These structures have great potential for
optoelectronic applications, one of which may be
solar cells - Standard solar cells have a theoretical upper
conversion rate of 33, the theoretical limit on
the conversion of sunlight to electricity is 67
22Light Absorption of Quantum Dots Definition of
a Quantum Dot9
23Light Absorption of Quantum Dots Definition of
a Quantum Dot9
24Light Absorption of Quantum Dots Definition of
a Quantum Dot9
25Light Absorption of Quantum Dots Formula7
- _
- Vav Average Dot Volume
- pfi 2d momentum matrix element
- a polarization of light
- N(??) density of states
26Light Absorption of Quantum Dots Formula12
- Transmission for Quantum dots.
- For transmission through n planes of dots, each
having the same dot density N and each dot
experiencing the same optical field amplitude,
the transmission fraction is - Tn(1-sN)n (1-nsN) (sN ltlt 1)
- s represents a cross section of the layer
27Light Absorption of Quantum Dots Comparison of
a versus Energy for Bulk Material and Quantum Dot9
28Light Absorption of Quantum Dots Comparison of
a versus Energy for Bulk Material and Quantum Dot
29Light Absorption of Quantum Dots Comparison of
a versus Energy for Bulk Material and Quantum Dot
30Light Absorption of Quantum Dots Comparison of
a versus Energy for Bulk Material and Quantum Dot7
31Light Absorption of Quantum Dots Comparison of
a versus Energy for Bulk Material and Quantum Dot7
32Introduction
- How Classical Solar Cells Operate
- Absorption Coefficient (a)
- Definition and Relevance of a
- Physical Techniques for Measuring a
- Light Absorption of Quantum Dot Layers
- Reasons for Interest Into Quantum Dot Light
Absorption - Definition of a Quantum Dot
- Formula for Light Absorption of a Quantum Dot
- Comparison of a versus Energy for Bulk Material
and Quantum Dot - Researchers working on Light Absorption of
Quantum Dots - Dr. Ryne Raffaelle
- Dr. Sheila Baily
- Problem Statement Determining the most
optically absorbent semiconductor material - Problem Solution
- Explanation of Theory
- Results
33Researchers Working on Light Absorption of
Quantum Dot Layers
- Dr. Sheila Bailey
- Using quantum dots in a solar cell to create an
intermediate band - IEEE Photovoltaic Specialist Conference (PVSC)
Executive Committee since 1987
http//www.grc.nasa.gov/WWW/RT2001/5000/5410bailey
1.html
34Researchers Working on Light Absorption of
Quantum Dot Layers11
- Dr. Ryne Raffaelle
- Rochester Institute of Technology
- NanoPower Laboratories
- Organic and Plastic Solar Cells Combined with
Quantum Dot Layers
http//www.physlink.com/News/Images/QDots1_lg.jpg
35Introduction
- How Classical Solar Cells Operate
- Absorption Coefficient (a)
- Definition and Relevance of a
- Physical Techniques for Measuring a
- Light Absorption of Quantum Dot Layers
- Reasons for Interest Into Quantum Dot Light
Absorption - Definition of a Quantum Dot
- Formula for Light Absorption of a Quantum Dot
- Comparison of a versus Energy for Bulk Material
and Quantum Dot - Researchers working on Light Absorption of
Quantum Dots - Dr. Ryne Raffaelle
- Dr. Sheila Baily
- Problem Statement Determining the most
optically absorbent semiconductor material - Problem Solution
- Explanation of Theory
- Results
36Problem Solution Explanation of theory
Photon Absorption
- z propagation direction
- nr refractive index
- omega frequency
- alpha absorption coefficient
- Laws of Conservation
- Energy
- Momentum
Photon Emission
Figures based on Singh textbook
37Problem Statement Determining the most
optically absorbent semiconductor bulk
- Consider InP and GaAs as being the available
semiconductors to create a solar cell. This
solar cell will be a hybrid, consisting of a
traditional solar cell created with either InP or
GaAs, and coating layers of quantum dots of
either InP or GaAs. If maximizing absorption is
the only criteria for designing the solar cell,
which material should be used for the bulk?
Which should be used for the quantum dot layers?
Assume the density of states for quantum dot
layers of both materials is equal and occurs at
the same point, E .1eV, and that the
polarization-momentum product sum is the same in
both cases.
38Problem Statement Determining the most
optically absorbent semiconductor bulk
- Absorption coefficient of InP and GaAs
- Required constants by material14
39Introduction
- How Classical Solar Cells Operate
- Absorption Coefficient (a)
- Definition and Relevance of a
- Physical Techniques for Measuring a
- Light Absorption of Quantum Dot Layers
- Reasons for Interest Into Quantum Dot Light
Absorption - Definition of a Quantum Dot
- Formula for Light Absorption of a Quantum Dot
- Comparison of a versus Energy for Bulk Material
and Quantum Dot - Researchers working on Light Absorption of
Quantum Dots - Dr. Ryne Raffaelle
- Dr. Sheila Baily
- Problem Statement Determining the most
optically absorbent semiconductor material - Problem Solution
- Explanation of Theory
- Results
40Problem Solution Results GaAs Bulk
41Problem Solution Results InP Bulk
42Problem Solution Results
43Problem Solution Results GaAs Quantum Dot
Layer
44Problem Solution Results InP Quantum Dot
Layer
45Conclusion
- How Classical Solar Cells Operate
- Absorption Coefficient (a)
- Definition and Relevance of a
- Physical Techniques for Measuring a
- Light Absorption of Quantum Dots
- Reasons for Interest Into Quantum Dot Light
Absorption - Definition of a Quantum Dot
- Formula for Light Absorption of a Quantum Dot
- Comparison of a versus Energy for Bulk Material
and Quantum Dot - Researchers working on Light Absorption of
Quantum Dots - Dr. Ryne Raffaelle
- Dr. Sheila Baily
- Problem Statement Determining the most
optically absorbent semiconductor material - Problem Solution
- Explanation of Theory
- Results
46References
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